The purpose of this project is to contribute to the understanding of hormone action on metabolic processes in breast tissue under normal conditions and to understand the failure of response under abnormal conditions. Among the topics studied are the response of mammary tissue in culture to hormones in terms of nucleic acid and protein synthesis. The kinds of proteins made by mammary tissue from normal non-pregnant, mid-pregnant, lactating animals and by neoplastic mammary tissue are being analyzed. Synthetic response to prolactin and steroid hormones is assessed by chemical and histochemical methods.